Defense Agency Director General Yoshinori Ono expressed regret Friday that the Self-Defense Forces were not able to conduct a nighttime rescue when a Japan Airlines jumbo jet crashed in Gunma Prefecture in August 1985, but emphasized that the military is now better able to deal with such catastrophes.

"At the time of the incident, the SDF did everything possible, mobilizing a combined 52,000 troops and using 7,800 vehicles and 1,200 aircraft. But they could not carry out nighttime rescue activities, and this is a major point to look back on," Ono told a news conference on the 20th anniversary of the tragedy, which claimed 520 lives.

He said there were many reasons why the SDF couldn't operate at night, citing equipment limitations, including the helicopters and night vision devices, and the chopper pilots' inability to hover well.

"I heard they gave their utmost efforts at the time, and I believe those who engaged in the rescue activities also felt sorry and frustrated," Ono said, adding the SDF's capabilities have advanced dramatically over the past two decades.

At a separate news conference, transport minister Kazuo Kitagawa stressed the need to ensure air safety.

"While convenience is important for air transportation, safety is the basic premise. I expect air carriers as well as their supervising administrative bodies to take sufficient measures in order to not repeat accidents," he said.

The crash claimed 520 lives. When rescuers reached the site after daybreak the next day, they found only four survivors. Others who had survived the crash but were injured died during the night awaiting rescue.